Adobe Photoshop CS5 for Photographers - Martin Evening [287]
There is not a lot you can do with the standard CMYK settings: you can make a choice from a handful of generic CMYK profile settings or choose ‘Custom CMYK…’. If you check the More options box, you'll be able to select from a more comprehensive list of CMYK profile settings in the extended menu (depending on what profiles are already in your ColorSync folder).
Creating a custom CMYK setting
Figure 12.34 shows the Custom CMYK dialog, which is better known as the familiar ‘classic’ Photoshop CMYK setup. Here, you can enter all the relevant CMYK separation information for a specific print job. Ideally you will want to save each purpose-built CMYK configuration as a separate color setting for future use and label it with a description of the print job it was built for.
Figure 12.34 When you select the ‘Custom CMYK…’ option at the top of the pop-up menu list, this opens the dialog box shown above, where you can enter the specific CMYK setup information to build a custom targeted CMYK setting. If you had previously clicked on the More Options button in the Color Settings, you will have a wider range of pre-loaded CMYK profile settings to choose from here.
Saving custom CMYK settings
Custom CMYK settings should be saved using the following locations: Library/ColorSync/Profiles/Recommended folder (Mac OS X); Windows/System32/Spool/Drivers/Color folder (PC).
Once you have configured a new CMYK workspace setting, this becomes the new default CMYK workspace that is used when you convert an image to CMYK mode. Note that altering the CMYK setup settings has no effect on the on-screen appearance of an already-converted CMYK file (unless there is no profile embedded). This is because the CMYK separation setup settings must be established first before you carry out the conversion.
Ink Colors
If you click on the Ink Colors menu, you can select one of the preset Ink Colors settings that are suggested for different types of printing. For example, European Photoshop users can choose from Eurostandard (coated), (uncoated), or (newsprint). These are just generic ink sets. If your printer can supply you with a custom ink color setting, then select ‘Custom…’ from the Ink Colors menu. This opens the dialog shown in Figure 12.35.
Figure 12.35 Here is a screen shot of the Custom Ink Colors dialog. For special print jobs such as where non-standard ink sets are used, or the printing is being done on colored paper, you can enter the measured readings of the color patches (listed here) taken from a printed sample on the actual stock that is to be used. You could measure these printed patches with a device such as the X-Rite Eye-One and use this information to create a custom Ink Colors setting for an individual CMYK press setup.
Dot gain
Dot gain refers to an accumulation of factors during the repro process that will make a dot printed on the page appear darker than expected. Among other things, dot gain is dependent on the type of press and the paper stock that's being used. The dot gain value entered in the CMYK setup determines how light or dark the separation needs to be. If a high dot gain is encountered, the separated CMYK films will need to be less dense so that the plates produced lay down less ink on the paper and produce the correctsized printed halftone dot for that particular type of press setup. You can see for yourself how this works by converting an image to CMYK using two different dot gain values and comparing the appearance of the individual CMYK channels. Although the dot gain value affects the lightness of the individual channels, the composite CMYK channel image is always